Transcript: The Difficulty of Arriving at a Vitamin D Recommendation
Figuring our what level of vitamin D supplementation is necessary to bring one’s level up to a specific blood level, like 30 nanograms per milliliter—the level associated with the longest lifespan—is not as easy as one might think. For example, here are seven people starting out with blood levels under the target of 30. They all got the exact same dose of vitamin D—1,600 IUs a day—and here’s what happened to their levels over the next six months.
One person’s blood levels tripled. Another even quadrupled. But in these three, even though they were all on the same dose, their blood levels hardly moved at all, and stayed under 30.
So, let’s say you’re trying to come up with a recommendation for people. Here’s a scatter plot of about 3,000 people. Blood level versus intake. So, people taking 10,000 IU a day average about a blood level of about 75, with 95% of people falling in between about 40 and 110.
If we want to choose a dose for which 95% of people reach the target of 30, we’d probably choose around 6,000 IU a day. But though that would get the most to the minimum, the average level would be over 50—which is higher than we’d like to see on the U-shaped vitamin D total mortality graph.
That’s equivalent to like 125 nanomoles per liter, which is off to the right of the graph. You can see why forming dietary recommendations is a formidable, and unenviable, task.
To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video. This is just an approximation of the audio contributed by veganmontreal.
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